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FADEC

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A Full Authority Digital Engine Control, known as FADEC, is a sophisticated system used in aviation. It manages every aspect of an aircraft engine's performance. The system consists of a digital computer called an Electronic Engine Controller (EEC) or an Engine Control Unit (ECU). It also includes various related accessories. The primary goal of a FADEC is to ensure the engine operates at maximum efficiency for any given flight condition. This technology is applied to both piston engines and jet engines.

EEC-Piston-Eng
EEC-Piston-Eng

The mechanism of a FADEC is incredibly fast and precise. It works by constantly receiving multiple input variables from the aircraft. These inputs include air density, engine temperatures, and engine pressures. It also tracks the position of the power lever requested by the pilot. The EEC analyzes this incoming data up to 70 times every second. Based on this analysis, the computer computes necessary changes to operating parameters. It can adjust fuel flow, the position of stator vanes, or the position of air bleed valves. The system even manages the processes of starting and restarting the engine.

There are important distinctions between different types of engine control systems. Originally, engines used simple mechanical linkages. Pilots or engineers moved physical levers to control fuel flow and power output. Later, engineers developed analogue electronic control. This used electrical signals to communicate settings but suffered from electronic noise and reliability issues. A true FADEC is unique because it has "full authority." This means there is no manual override for the engine's operating parameters. If a system allows for manual intervention, it is simply called an EEC or an ECU. An EEC is a component of a FADEC, but it is not a FADEC on its own.

The history of this technology shows a steady move toward automation. In the 1960s, full authority analogue control was used in the Concorde's Olympus 593 engine. However, the digital era began to take shape in 1968. During that year, Rolls-Royce and Elliott Automation tested a digital system on a Rolls-Royce Olympus Mk 320. In the 1970s, NASA and Pratt & Whitney conducted experiments with a FADEC on an F-111 aircraft. These experiments led to the Pratt & Whitney F100 and the PW2000 becoming the first military and civil engines with FADEC. The first FADEC to actually enter service was for the Rolls-Royce Pegasus engine used in the Harrier II.

FADEC provides several significant advantages for modern flight. It offers automatic protection against operating outside of safe limits. For example, it can be programmed to prevent an engine from exceeding specific temperatures. This happens automatically without any pilot intervention. The system also allows for "care-free" engine handling, which guarantees specific thrust settings. It enables manufacturers to use a single engine type for many different requirements just by reprogramming the software. Additionally, the number of parameters monitored by the system increases by an order of magnitude. This reduces the workload for flight crews, as they no longer need to monitor every small detail manually.

Safety is a critical concern when automation controls an engine. To prevent a single point of failure, FADEC uses redundancy. This means the system includes two or more separate but identical digital channels. Each channel is capable of providing all engine functions without restriction. This creates a "fault tolerant" system, which can continue to operate safely even if a fault occurs. However, total failure is a serious risk. If a total FADEC failure occurs, the engine fails. In such a case, pilots have no manual controls for throttle or engine restarts. One notable incident occurred on 9 May 2015, when an Airbus A400M crashed in Seville, Spain. This crash was caused by incorrectly installed engine control software.

FADEC technology connects deeply to the field of systems engineering. Because these systems are safety-critical, they require formal engineering processes to design and test. Engineers use specialized tools like Model-Based Systems Engineering (MBSE) to develop the software. An example of such a tool is SCADE, which is used for application development. Modern research is even looking at new ways to organize these systems. NASA has analyzed a distributed FADEC architecture for helicopters. This would move away from the current centralized architecture to provide more flexibility and lower costs.

EEC-Piston-Eng
EEC-Piston-Eng
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